Aerospace-grade composite resins typically consist of a blend of epoxy monomers including, without limitation, multifunctional epoxy monomer(s) and a bi-functional amine monomer(s). To achieve a reasonable rate of reaction at an elevated temperature, resin systems frequently incorporate catalyst molecules that will accelerate the epoxy-amine reaction to a desirable cure. It is desirable to maintain room temperature tack of an adhesive for the longest possible duration, while still providing a fast rate of reaction at elevated temperatures. This can be accomplished by segregating most of the catalyst from the resin at room temperature, but it must be accomplished in a way that causes a catalyst to be dispersed throughout the resin at an elevated temperature.
Traditional epoxy resins, and other adhesive resin curing systems are typically governed by understood curing kinetics. In the case of epoxy resins, the curing of epoxy resin systems is often governed by the curing kinetics of epoxy resins with multifunctional amines or thiol reactive groups that are often combined with a catalyst. Such adhesive systems have limited manufacturing flexibility due to the relationship between work life of the adhesive and cure time. Work life is understood to be the amount of time available to make an active epoxy resin-based adhesive, followed by applying an epoxy-based adhesive to the desired end use before the epoxy resin-based adhesive “sets” or “cures” to the point where it becomes unworkable to apply (because the epoxy has hardened and will no longer “flow”). Therefore, highly accelerated epoxy resin adhesive system cure times inevitably lead to shorter, and often impractical, pot life times. Conversely, an epoxy resin system having a longer work life takes a longer time to cure. Longer adhesive system cure times increase manufacturing time on a production line, and otherwise lead to increased production inefficiency.
In addition, known epoxy resin- and acrylate resin-based adhesive systems may require heat to activate a system catalyst and “trigger” the curing reaction. In many manufacturing systems for large components, including, without limitation, those components typically manufactured in connection with the aerospace industry, presenting equipment capable of supplying evenly applied heat to such components of a certain dimension to trigger adhesive curing is not possible, not practical, or would significantly increase manufacturing cost.
An efficient and cost-effective on-demand adhesive system that is both rapid curing, and that also has a significantly long work life would be useful, cost-effective and highly advantageous.